Having a problem airbrushing this model

Hi, I am so much problems painting this model I have painted it seven times now and keep getting the same result, I haven't used a airbrush in decades, but whatever I try I seem to be getting a uneven mat result the paint I used is Humbrol mat enamel with there own thinners at a ratio of 50/50, Also I have adjusted my psi from 15 to 25 with no difference. I also tried Revel enamel but it came out exactly the same. I am trying to make this for my daughters birthday who is a big star wars fan but am running out of time. Thanks.

Hard to say what is causing the issue but I kinda like how it looks actually. 25 psi is getting up there for pressure so I'd go back to the 15 you started with. Recoating over a problematic first coat often won't solve your problem as the first coat sets the tone for the rest. Normally I'd recommend stripping all the paint, thoroughly cleaning the surface, and restarting but the texture is going to be an issue for that and it may just make things worse.

I'd suggest you leave it alone. It will look much better once the decals are on.

First off, welcome to the site. For me personally, I would call it weathering but I'm not sure what its really supposed to look like